Coordinated Resuscitation Perfusion Support

ABSTRACT

This document relates to systems and techniques for the treatment of a cardiac arrest victim via electromagnetic stimulation of physiologic tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a utility from a provisional of U.S. Application Ser. No.61/473,273 filed Apr. 8, 2011. All subject matter set forth in the abovereferenced application is hereby incorporated by reference into thepresent application as if fully set forth herein.

TECHNICAL FIELD

This document relates to systems and techniques for the treatment of acardiac arrest victim via electromagnetic stimulation of physiologictissue.

BACKGROUND

Cardiac Arrest, or Sudden Death, is a descriptor for a diversecollection of physiological abnormalities with a common cardiacetiology, wherein the patient typically presents with the symptoms ofpulselessness, apnea and unconsciousness. Cardiac arrest is widespread,with an estimated 300,000 victims annually in the U.S. alone and asimilar estimate of additional victims worldwide. Early defibrillationis the major factor in sudden cardiac arrest survival. There are, infact, very few cases of cardiac arrest victims saved which were nottreated with defibrillation. There are many different classes ofabnormal electrocardiographic (ECG) rhythms, some of which are treatablewith defibrillation and some of which are not. The standard terminologyfor this is “shockable” and “non-shockable” ECG rhythms, respectively.Non-shockable ECG rhythms are further classified into hemodynamicallystable and hemodynamically unstable rhythms. Hemodynamically unstablerhythms are those which are incapable of supporting a patient's survivalwith adequate blood flow (non-viable). For example, a normal sinusrhythm is considered non-shockable and is hemodynamically stable(viable). Some common ECG rhythms encountered during cardiac arrest thatare both non-shockable and hemodynamically unstable are: bradycardia,idioventricular rhythms, pulseless electrical activity (PEA) andasystole. Bradycardias, during which the heart beats too slowly, arenon-shockable and also possibly non-viable. If the patient isunconscious during bradycardia, it can be helpful to perform chestcompressions until pacing becomes available. Idioventricular rhythms, inwhich the electrical activity that initiates myocardial contractionoccurs in the ventricles but not the atria, can also be non-shockableand non-viable (usually, electrical patterns begin in the atria).Idioventricular rhythms typically result in slow heart rhythms of 30 or40 beats per minute, often causing the patient to lose consciousness.The slow heart rhythm occurs because the ventricles ordinarily respondto the activity of the atria, but when the atria stop their electricalactivity, a slower, backup rhythm occurs in the ventricles. PulselessElectrical Activity (PEA), the result of electro-mechanical dissociation(EMD), in which there is the presence of rhythmic electrical activity inthe heart but the absence of myocardial contractility, is non-shockableand non-viable and would require chest compressions as a first response.Asystole, in which there is neither electrical nor mechanical activityin the heart, cannot be successfully treated with defibrillation, as isalso the case for the other non-shockable, non-viable rhythms. Pacing isrecommended for asystole, and there are other treatment modalities thatan advanced life support team can perform to assist such patients, e.g.intubation and drugs. The primary examples of shockable rhythms that canbe successfully treated with defibrillation are ventricularfibrillation, ventricular tachycardia, and ventricular flutter.

Normally, electrochemical activity within a human heart causes theorgan's muscle fibers to contract and relax in a synchronized manner.This synchronized action of the heart's musculature results in theeffective pumping of blood from the ventricles to the body's vitalorgans. In the case of ventricular fibrillation (VF), however, abnormalelectrical activity within the heart causes the individual muscle fibersto contract in an unsynchronized and chaotic way. As a result of thisloss of synchronization, the heart loses its ability to effectively pumpblood. Defibrillators produce a large current pulse that disrupts thechaotic electrical activity of the heart associated with ventricularfibrillation and provides the heart's electrochemical system with theopportunity to re-synchronize itself. Once organized electrical activityis restored, synchronized muscle contractions usually follow, leading tothe restoration of effective cardiac pumping.

With the first clinical use in humans described in 1956 by Dr. PaulZoll, transthoracic defibrillation has become the primary therapy forcardiac arrest, ventricular tachycardia (VT), and atrial fibrillation(AF). Monophasic waveforms dominated until 1996, when the first biphasicwaveform became available for clinical use. Actualsurvival-to-hospital-discharge rates remain an abysmal ten percent orless. Survival rates from cardiac arrest remain as low as 1-3% in majorU.S. cities, including those with extensive, advanced pre-hospitalmedical care infrastructures.

The importance of good quality, deep compressions on improving survivalhas recently been rediscovered by the clinical community. The AmericanHeart Association, in their most recent 2010 Guidelines, state, “Thescientists and healthcare providers participating in a comprehensiveevidence evaluation process analyzed the sequence and priorities of thesteps of CPR in light of current scientific advances to identify factorswith the greatest potential impact on survival. On the basis of thestrength of the available evidence, they developed recommendations tosupport the interventions that showed the most promise. There wasunanimous support for continued emphasis on high-quality CPR, withcompressions of adequate rate and depth, allowing complete chest recoil,minimizing interruptions in chest compressions and avoiding excessiveventilation.”

In spite of the recommendations from the AHA and other recognizedclinical bodies that good quality compressions with no pausing isimportant for cardiac arrest survival, compressions without pauses isactually very difficult to achieve, even with clinical use protocolsthat are specifically designed to achieve continuous compressions, withno ventilation pauses. It has been shown that CPR fraction, thepercentage of time during the course of resuscitation during whichcompressions are present, is only 60-70% even for those systems whichutilize the continuous compression approach to eliminate the ventilationpauses. The CPR fraction can be further increased to 80-85% whendefibrillators are utilized that incorporate a motion sensor under therescuers hands and provide real time feedback to the rescuer on thequality of their compressions (RealCPRHelp, ZOLL Medical, Chelmsford).

Devices for augmentation of circulation by pacing of asystole andbradycardia combined with defibrillation have been available for anumber of years. U.S. Pat. No. 4,088,138 describes a device thatautomatically paces a patient either before or after a defibrillationshock when either profound bradycardia or asystole is detected.

Use of electrical stimulation of skeletal muscles to deliver blood flowsimilar to conventional sternal chest compressions during CPR has beendescribed by Wang and colleagues in Crit Care Med 2008;36[Suppl.]:S458-S466. As the authors note, however, the method is oflimited value as skeletal muscle fatigue onset is fairly rapid, evenunder optimal lab conditions; fatigue onset was found to be less thanone minute in most cases. It should be noted that a typical clinicallyadvised interval for chest compressions is two minutes, thus efficaciousstimulation will not reliably be achieved for even one full CPRinterval. The technique is further elucidated, for example, in U.S. Pat.Nos. 5,782,883, 6,185,457, 5,978,703, 6,314,319, and 6,567,607.

There are two primary mechanisms for generation of blood flow duringchest compression in cardiopulmonary resuscitation (CPR): the cardiacpump mechanism and the thoracic pump mechanism. “The cardiac pumphypothesis holds that blood flow is generated during closed-chestcompressions when the heart is squeezed between the sternum and thevertebral column. This mechanism of flow implies that ventricularcompression causes closure of the atrioventricular valves and thatejection of blood reduces ventricular volume. During chest relaxation,ventricular pressure falls below atrial pressure, allowing theatrioventricular valves to open and the ventricles to fill. Thissequence of events resembles the normal cardiac cycle and occurs duringcardiac compression when open-chest CPR is used.” [Peter Trinkaus,Charles L. Schleien, Physiologic Foundations of CardiopulmonaryResuscitation, In: Bradley P. Fuhrman, MD, and Jerry J. Zimmerman, MD,PhD, Editor(s), Pediatric Critical Care (Third Edition), Mosby,Philadelphia, 2006, Pages 1795-1823, ISBN 978-0-32-301808-1, DOI:10.1016/B978-032301808-1.50121-8.] Trinkaus goes on to say, “Duringnormal cardiac function, the lowest pressure in the vascular circuitoccurs on the atrial side of the atrioventricular valves. This lowpressure compartment is the downstream pressure for the systemiccirculation, which allows venous return to the heart. Angiographicstudies show that blood passes from the venae cavae through the rightheart into the pulmonary artery and from the pulmonary veins through theleft heart into the aorta during a single chest compression.Echocardiographic studies show that, unlike normal cardiac activity orduring open chest CPR, during closed-chest CPR in both dogs and humansthe atrioventricular valves are open during blood ejection and aorticdiameter decreases rather than increases during blood ejection. Thesefindings during closed-chest CPR support the thoracic pump theory andargue that the heart is a passive conduit for blood flow.” (FIG. 1). Inpractice, the mechanism of blood flow generation during chestcompressions is both cardiac and thoracic, with the relative proportionof effect being a function of the patient's individual vascular andvalvular state as well as the performance parameters of the chestcompression, particularly with regard to the depth, rate and release ofthe compression.

A typical patient will require approximately 100-200 pounds of force forthe rescuer to compress the sternum to the recommended depth of 2inches. The guidelines further recommend that the rate of compressionsbe at one compression every 600 milliseconds. During a normalresuscitation, as a result of this level of exertion, the rescuerresponsible for performing chest compressions will fatigue from theeffort even in as short a time as one minute. In response to thefatigue, the rescuer will respond by either switching roles with anotherrescuer, by pausing compressions, or by reducing their level of exertionwhich will inevitably result in insufficient compression effectiveness.In the case of switching rescuers, this procedure will result in pausesin compressions of at least 10 seconds and potentially 30 seconds if theaction is performed inefficiently. During this period of pausing, thepatient is of course not receiving the life-saving therapy of chestcompressions, and no blood is being delivered to the heart, brain andother vital organs. It would thus be desirable to have an automaticmeans of delivering perfusion during periods of switching rescuers,periods of rescuer fatigue, pauses and other lapses in compressionquality.

Attempts to use electrical stimulation for ventilation during CPR havealso been described in U.S. Pat. No. 6,213,960 for electrostimulation inconjunction with a chest compression device and stimulation of nervescontrolling ventilation. U.S. Pat. Nos. 6,463,327 and 6,234,985 alsodescribe the use diaphragmatic stimulation by the phrenic nerve in orderto augment venous return and hemodynamics during CPR. The use of phrenicstimulation for cardiac arrest victims has not been found to beparticularly effective for several reasons: 1) the patient has beenanoxic for an extended period during cardiac arrest prior to treatment,resulting in degraded metabolic status of the whole nervous system,including the phrenic nerve, making electrostimulation much lesseffective than with conscious patients; 2) non-invasive locations forstimulation electrodes on the thorax also stimulate the intercostalmuscles that cause exhalation, in direct opposition to the inspiratoryeffect caused by phrenic stimulation and its associated diaphragmaticcontraction; and 3) while the phrenic nerve in the neck can bestimulated non-invasively, is often difficult to locate, particularly inthe pre-hospital environment and under the acute, emergent situation ofcardiac arrest.

SUMMARY

This document describes systems and techniques that may be used toprovide improved chest compression for a patient or victim who issuffering from ventricular fibrillation or a similar malady.

In some aspects, a medical system for providing electromagneticstimulation of a patient includes a sensor positioned to sense thepresence of manual chest compressions administered to the patient by arescuer. The system also includes a processor arranged to receive datagenerated by the sensor and detect changes in the administration of thechest compressions and circuitry configured for delivery ofelectromagnetic stimulation to the patient to stimulate blood flow inthe patient upon detection of the change in the administration of thechest compressions.

Embodiments can include one or more of the following.

The changes can include a degradation in the quality of the chestcompressions.

The degradation in the quality of the chest compressions can include achange in depth of the chest compressions.

The degradation in the quality of the chest compressions can include achange in compression release of the chest compressions.

The processor can be configured to detect changes in the administrationof the chest compressions by detecting an absence of chest compressionsfor a period of time greater than a threshold.

The processor can be configured to detect changes in the administrationof the chest compressions by detecting an absence of chest compressionsfor a period of time greater than a 2 seconds.

The processor can be configured to detect changes in the administrationof the chest compressions by comparing data generated by the sensorduring a first time period with data generated by the sensor during asecond time period that occurs after the first time period.

The sensor can be configured to detect motion of the patient's sternum.

The sensor can include a motion sensor, a pressure sensor, and/or avelocity sensor.

The circuitry configured for delivery of electromagnetic stimulation canbe further configured to deliver the electromagnetic stimulationautomatically and without user intervention.

The circuitry configured for delivery of electromagnetic stimulation caninclude an electrode assembly affixed to the patient's thorax.

The electrode assembly can be removably affixed to the patient's thorax.

The circuitry can include circuitry configured to deliver a pulse packetof 100-200 microsecond duration pulses with inter-pulse spacing of 5-15milliseconds and an amplitude of 300-700 volts.

The circuitry can include circuitry configured to deliver a pulse packetof 20-1000 microsecond duration pulses with a duty cycle of 2-95% and anamplitude of 50-2000 volts.

The system can also include a display device configured to visuallyprompt the rescuer to resume manual chest compressions upon initiationof delivery of the electromagnetic stimulation to the patient.

The system can also include a speaker configured to provide an audioprompt the rescuer to resume manual chest compressions upon initiationof delivery of the electromagnetic stimulation to the patient.

The processor can be configured to detect changes in the administrationof the chest compressions by detecting a degradation in the quality ofchest compressions.

The circuitry can be configured to deliver the electromagneticstimulation simultaneously with the administration of the manual chestcompressions by the rescuer upon detection of the degradation in thequality of chest compressions.

In some additional aspects, an external defibrillator for providingcontrolled shock to victims of heart problems includes an electricalstorage device capable of delivering a defibrillating shock to apatient. The defibrillator also includes a proximity sensor configuredto determine a location of the rescuer's hands relative to the patientand a controller programmed to calibrate the proximity sensor byanalyzing data from the proximity sensor received during a time periodcorresponding to delivery manual administration of chest compressions bythe rescuer and to cause the electrical storage device to deliver adefibrillating shock to the patient based at least in part on data fromthe proximity sensor.

Embodiments can include one or more of the following.

The proximity sensor can be a capacitance sensor.

The proximity sensor can be further configured to detect removal of therescuer's hands from the patient.

The controller can be further configured to cause the electrical storagedevice to deliver a defibrillating shock to the patient upon detectingthe rescuer is at least two inches away from the patient.

The proximity sensor can be an ultrasonic sensor.

The proximity sensor can be a light emitter-receiver pair.

In some additional aspects, a medical system for providingelectromagnetic stimulation of a patient can include a first set ofelectrodes configured to be located to initiate blood flow based on acardiac pump mechanism and a second of electrodes configured to belocated to initiate blood flow based on a thoracic pump mechanism. Thesystem can also include a controller programmed sequence delivery ofelectrical energy from the first set of electrodes and the second set ofelectrodes to generate dual-stage electrical stimulation configured tocause blood flow in the patient.

Embodiments can include one or more of the following.

The dual-stage electrical stimulation can include a first stage duringwhich the controller is configured to activate the first set ofelectrodes and a second stage during which the controller is configuredto activate the second set of electrodes.

The second set of electrodes can be configured to be positioned atlocations that primarily stimulate thoracic muscle groups that duringcontraction produce blood flow primarily via the thoracic pumpmechanism.

The second set of electrodes can be configured to be positioned on theleft and right sides of the patient at the bottom of the rib cage.

The controller can be further programmed sequence delivery of electricalenergy from the first set of electrodes and the second set of electrodesby delivering a pulse from the second set of electrodes 100-500milliseconds after delivering a pulse from the first set of electrodes.

The controller can be further programmed sequence delivery of electricalenergy from the first set of electrodes and the second set of electrodesby delivering a pulse from the second set of electrodes 100-200milliseconds after delivering a pulse from the first set of electrodes.

In some additional aspects, a method for promoting sternocostalinhalation includes electrically stimulating a first set muscles thatattach to some portion of the ribs and electrically stimulating a secondset of muscles that when contracted cause an opposing motion of thespine.

Embodiments can include one or more of the following.

Electrically stimulating the second set of muscles can cause an opposingmotion of the spine in either the sagittal or transverse axis.

Electrically stimulating the first set muscles can include electricallystimulating the first set muscles using a first cathodal electrodelocated above the right rhomboid major muscle and a second cathodalelectrode located above the left rhomboid major.

Electrically stimulating the first set muscles further can includeelectrically stimulating the first set muscles using an anodalelectrodes located above the scapula.

Electrically stimulating the second set of muscles can includeelectrically stimulating the second set of muscles using a firstcathodal electrode located above the left serratus anterior muscle and asecond cathodal electrode located above the right serratus anteriormuscle.

Electrically stimulating the second set of muscles can includeelectrically stimulating the second set of muscles at a time subsequentto electrically stimulating the first set muscles.

Electrically stimulating the first and second sets of muscles caninclude electrically stimulating the first and second sets of musclesduring an upstroke of a manual chest compression.

Electrically stimulating the first and second sets of muscles caninclude electrically stimulating the first and second sets of musclesusing a pulse width modulated waveform.

Electrically stimulating the first and second sets of muscles caninclude electrically stimulating the first and second sets of musclesusing a waveform comprising a ramped leading edge.

DESCRIPTION OF THE FIGURES

FIG. 1 shows the two primary modes of blood flow during CPR.

FIGS. 2 a and 2 b shows anterior and posterior electrode assemblies,respectively, applied to a patient.

FIG. 3 is a flow chart of a method for generating electromagneticstimulation pulses.

FIG. 4 is a flow chart of a method for detecting and using a rescuer'sproximity to determine when to deliver a defibrillation shock.

FIG. 5 shows the electrode placement for stimulation to enhance thoracicvolume.

FIG. 6 shows placement of the electrode within a wearable defibrillatorharness.

FIG. 7 is a block diagram of the system.

FIG. 8 shows a schematic for an E-field proximity sensor 216.

DETAILED DESCRIPTION

This document describes mechanisms by which chest compressions for apatient suffering from sudden cardiac arrest can be coordinated withelectromagnetic stimulation of various locations on the patient'sthorax.

Good quality compressions with little or no pausing (e.g., substantiallycontinuous administration of compressions) are important for cardiacarrest survival. However, it is difficult for the average rescuer toprovide continuous, high quality manual compressions without pauses.Systems and methods are described herein to automatically detect thecessation or pausing of a rescuer's manual administration of chestcompressions and supplement the treatment of the patient with electricalstimulation during the time periods of such pauses. The electricalstimulation begins automatically based on detected characteristicsrelated to the manual administration of chest compressions such that thetime period between cessation or pausing of the manual chestcompressions and administration of the electrical stimulation is brief(e.g., less than 10 seconds, less than 5 seconds, less than 3 seconds).Examples of such electrical stimulation include electrical stimulationof skeletal muscles to deliver blood flow similar to conventionalsternal chest compressions during CPR and two-stage stimulation tosequentially apply electrical stimulation to encourage circulation basedon the cardiac pump mechanism and thoracic pump mechanism both of whichare described in more detail below.

Due to the rapid onset of skeletal muscle fatigue which reduces theutility of the electrical stimulation, the period of time that the bloodflow is stimulated by the application of electrical stimulation limited(e.g., less than one minute, less than 30 seconds). In order toencourage the rescuer to resume manual chest compressions, the systemcan provide visual and/or audio prompts to the rescuer instructing therescuer to resume manual chest compressions shortly after beginningelectrical stimulation (e.g., 5 seconds after detection of cessation ofeffective compressions or beginning electrical stimulation, 10 secondsafter detection of cessation of effective compressions or beginningelectrical stimulation, 20 seconds after detection of cessation ofeffective compressions or beginning electrical stimulation).

In some examples, the electrical stimulation can be administered by, forexample, an anterior electrode assembly (AEA) 100 affixed to thepatient's 102 thorax as described in relation to FIGS. 2A and 2B below.FIGS. 2A and 2B show anterior and posterior electrode assemblies,respectively, applied to a patient.

The AEA 100 is composed of a defibrillation/pacing/monitoring electrode101 known to those skilled in the art, composed of a conductive adhesivegel in contact with the patient's skin, typically also a conductivemetallic surface on the conductive gel for distributing the currentdelivered by the stimulation device 103, and an insulative top layer.Thus, the AEA 100 can be removably affixed to the patient's thorax. Ahousing 104 containing a motion sensor along with power and signalconditioning electronics is positioned on the patient's sternum, and isused to measure the motion of the sternum during CPR chest compressions.The motion sensor may be an accelerometer as is used commercially indevices of this type (ZOLL CPR Stat-Padz, Chelmsford, Mass.) or may be apressure sensor, a velocity sensor such as those employing atime-varying magnetic flux and coil arrangement or other varied motionsensors. Defibrillator 10 processes conditioned motion sensor signal viathe Sternal Motion analysis subsystem 3 to determine when the rescuerhas ceased chest compressions, paused in the administration of chestcompressions, or is no longer administering effective chestcompressions. The Sternal Motion analysis subsystem 3 can be, forexample, a software function that is part of the software code forrunning the Defibrillator 10 in general, or may be specialized hardwareeither in the defibrillator or in the housing 104 that may communicateto the defibrillator Microprocessor 14 via, for instance, a serialcommunication channel such as USB, RS232 or Bluetooth. During the courseof any typical CPR interval, the duration of which is typically on theorder of 2 minutes, a rescuer may stop briefly at multiple points,sometimes for as little as 3-10 seconds. Each of these pauses has asignificant adverse impact on the potential of the patient to achievereturn of spontaneous circulation (ROSC) during the course of theresuscitation attempt. Referring now to FIG. 3, the microprocessor 14analyzes signals to determine when the rescuer has paused or ceasedchest compressions (130). When the Microprocessor 14 detects a pause inthe manual chest compressions of more than a threshold length of time(132), for example, more than about 2 seconds, more than about 3seconds, more than about 5 seconds, the system will automatically beginto deliver electromagnetic stimulation pulses via the electrodes 101 and101 b (134). In animal testing it was found that the optimal stimulationwaveform was a pulse packet of 100-200 microsecond duration pulses withinter-pulse spacing of 10 milliseconds and a train length of 5-10 pulsesand an amplitude of approximately 500 Volts. At the same time thatelectromagnetic perfusion stimulation (EPS) is initiated, thedefibrillator begins prompting the user that electrical compressionshave been initiated temporarily and/or to prompting the user to resumemanual chest compressions (136). The prompting may be either visual texton the display screen of the defibrillator or in the form of speechprompts. The duration of the EPS will be limited to some period of timetypically not to exceed 1 minute, though at minimum, the EPS durationmay be limited to as short a time period as 5-10 seconds. A period ofapproximately 15 seconds will be particularly helpful when the rescuerperforming compressions has fatigued and the rescuers are switchingroles, or when the rescuer performing compressions is pausing due eitherto fatigue or being distracted by some event in the rescue environment,an alarm on the defibrillator or having to perform a function likeendotracheal intubation. The system continues to monitor the signals todetermine when the rescuer resumes manual chest compressions. Upondetection that the rescuer has resumed manual chest compressions (138),the system ceases providing the electrical compressions (140) andresumes monitoring the quality of the manual chest compressions (130).

By analyzing the compression characteristics, it is possible todetermine whether or not the rescuer is fatigued. For example, in theexample provided above, the system can detect fatigue based on adegradation of the quality of chest compressions in addition to orinstead of detecting the complete cessation of administration of chestcompressions and administer electrical stimulations based on thedetection of such changes in the chest compression quality. Generally,methods for detecting fatigue can include determining initialstatistical characteristics of the rescuer's compressions, and thenanalyzing the compression characteristics for any significant, sustaineddegradations. For instance, the known techniques such as change pointanalysis such as that described by Basseville (Basseville M, Nikiforov IV. Detection of Abrupt Changes: Theory and Application. Engelwood, N.J.:Prentice-Hall 1993) or Pettitt (Pettitt A N. A simple cumulative sumtype statistic for the change point problem with zero-one observations.Biometrika 1980; 67:79-84.) Other known methods such as Shewhart controlcharts may be employed for first detecting changes in thecharacteristics and then assessing whether the change detected is both adegradation and of a sufficient magnitude to cause the defibrillator tofirst initiate prompts to improve that particular aspect of thecompression characteristic and then if the quality does not improvesufficiently then initiate temporary EPS as a stop-gap measure anddeliver a prompt to switch rescuers.

In some embodiments, the EPS may be delivered substantially simultaneousto the manual compressions delivered by the rescuer, particularly in thecase where the compression are still ongoing, but are of diminishedquality. In order to prevent electrical shock to the rescuer, the sensorhousing 104 and electrode 101 may be integrated into a thin, flexibledielectric insulative sheet 105. Mylar plastic may be used for such amaterial, preferably of about 0.5 mil thickness.

In some embodiments, the sensor housing and electrodes are configured toensure that the rescuer's hands have been removed from the patient(e.g., are not in contact with the patient) prior to administration of adefibrillation shock and or delivery the electrical stimulations forelectrical compressions. For example, the sensor housing can include aproximity sensor (e.g., a capacitance sensor) that determines whether arescuer is in contact with the patient and prohibits delivery ofelectrical current to the patient when the rescuer is in contact withthe patient. In some additional examples, as described in more detailbelow, the system can be configured to coordinate the delivery of thedefibrillation shock with the detection that the rescuer has removedhis/her hands from the patient. For example, the defibrillation shockcan be delivered automatically and without requiring further user actionupon detection that the rescuer has removed his/her hands from thepatient.

More particularly, the sensor housing 104 may also contain a proximitysensor 216 for measuring the location of the rescuer's hands (e.g., asshown in FIGS. 7 and 8). This measurement of rescuer hand location maybe used in several possible ways. In cases where the electrode assemblyAEA 100 does not incorporate an insulative sheet 105, the hand locationmeasurement may be used to hold off EPS (e.g., prohibit delivery ofelectrical pulses) until the rescuer has removed their hands from thepatient's chest. Additionally, upon detection of fatigue or cessation ofmanual chest compressions, the device can provide audio and/or visualprompting to the rescuer instructing them to remove their hands frompatient's chest until such time as they do remove their hands. The handmeasurement may also be used as a triggering mechanism for delivery oftherapeutic electromagnetic energy (e.g., defibrillation shock) to thepatient. It is believed that automatically delivering the therapeuticelectromagnetic energy upon detection of the removal of the rescuer'shands can reduce the time between cessation of manual chest compressionsand delivery of the therapeutic electromagnetic energy. For example, thedefibrillator may be charged during delivery of the manual chestcompressions such that the therapeutic electromagnetic energy can bedelivered immediately (e.g., within less than 1 second) after thecessation of manual chest compressions.

Without the automatic detection of the removal of the rescuer's handsand using the detection to trigger the delivery of the therapeuticelectromagnetic energy, when treating a patient who has a shockablerhythm, the defibrillator may be charged by a second rescuer while thefirst delivers ongoing compressions. At the moment for delivering ashock, however, the first rescuer controlling the defibrillator willhave the rescuer delivering stop compressions until after the shock isdelivered by the first rescuer. This involves a set of clearancecommands between the two rescuers, such as saying, “Stand Clear. You'reclear. I'm clear. We're all clear”, then pressing the shock button whenthe first rescuer has made sure that no one is touching the patient.This process can cause for period of no delivery of therapeuticcompressions for 5-10 seconds (e.g., the time lapse between cessation ofchest compressions until the delivery of the electromagnetic energy canbe 5-10 seconds). With the automatic detection of the rescuer proximityto the patient, the first rescuer arms the defibrillator, and then thesecond rescuer who has their hands on the sensor housing 104, deliveringthe compressions, actually causes the defibrillator to deliver thedefibrillation shock by simply lifting their hands from off the sensor.Thus, the electromagnetic energy is automatically delivered upondetection of the removal of the rescuer's hands from the patient. Thisis believed to be particularly effective because the only person whowill be in contact with the patient is the compressor at that point, andthey are in the best position to assess whether anyone else might be incontact. When the rescuer lifts their hands off the sensor housing 104,the proximity sensor 216 detects that the rescuers hands have beenremoved from proximity of the patient and then automatically deliversthe shock.

In some embodiments, E-field sensing such as that provided by theMC33941 (Freescale Semiconductor, document Number: MC33941, Rev 4) canbe used (e.g., as shown in FIG. 8). Because this method of proximitysensing is fundamentally a measure of stray capacitance embodied by therescuer's hands, it is important to calibrate to each rescuer because ofthe variable capacitance interjected by the use of medical gloves, etc.Calibration is accomplished automatically during the time thatcompressions are occurring. Because the sensor housing is beingdepressed during compressions, it can be safely assumed, particularly atthe time when compression is at its deepest point, that the rescuerhands are in direct contact with the surface of the sensor housing 104.The measured capacitance at that point is taken as the zero-distancereference point.

There are additional benefits beyond minimizing the compression pausesduring defibrillation. For instance, it is believed that synchronizingthe defibrillation shock to the early phase of the compression upstrokesignificantly improves shock efficacy. By shocking immediately afterdetection of loss of rescuer hand contact, the defibrillation shock canbe timed to the optimal phase of the compression cycle.

In some additional embodiments, rather than delivering thedefibrillation shock immediately upon detection of removal of therescuer's hands from the patient, one to ten EPS pulses may also bedelivered immediately prior to the defibrillation shock, after theproximity sensor 216 and processor have detected loss of contact withthe rescuer's hands. The defibrillation shock is then synchronized tothe optimal phase of the final EPS pulse.

Alternatives to the E-field proximity sensor 216 are ultrasonic sensorssuch as the MINI_A PB Ultrasonic transducer (SensComp, MI) that has ameasurement range of 1-12 inches. Alternatively, a lightemitter-receiver pair may be located on the rescuer-facing upper surfaceof the sensor housing 104 and be used to detect the instant there is aphysical separation between surface of the sensor housing 104 and therescuer's hands.

FIG. 4 is a flow chart of a method for automatically delivering adefibrillation shock based on the detection of the removal of arescuer's hands from a patient. The system performs a calibration of aproximity sensor by setting a reference point based on a capacitancemeasurement when compressions are being administered (142). The systemanalyzes ongoing capacitance measurements to detect changes incapacitance from reference point (144). Upon detection of significantchange in capacitance (e.g., a change indicative of removal of therescuer's hands from the patient), the system automatically delivers adefibrillation shock to the patient (146).

As discussed herein, in some embodiments, electrical stimulation can beused to cause blood flow in a patient similar to manual chestcompressions to supplement manual delivery of manual chest compressionsduring periods of rescuer fatigue or cessation of chest compressiondelivery. In some embodiments, the electrical stimulation can include atwo-stage electrical stimulation configured to electrically initiateblood flow based on the cardiac pump mechanism and the thoracic pumpmechanism that are believed to be the two primary mechanisms forgeneration of blood flow during chest compressions in cardiopulmonaryresuscitation (CPR). The two-stage electrical stimulation uses two setsof electrodes with a first set of electrodes located to stimulate musclegroups that during contraction produce blood flow primarily via thecardiac pump mechanism and a second set of electrodes located tostimulate muscle groups that during contraction produce blood flowprimarily via the thoracic pump mechanism.

As the location of the electrode 101 a is positioned so as to deliverEPS whose mechanism of blood flow is primarily via the so-called cardiacpump mechanism, it is optimal to also provide for additional EPSelectrode locations that primarily stimulate thoracic muscles that, whencontracting, will generate blood flow primarily via the so-calledthoracic pump mechanism. Preferably, this location at on the left andright sides of the patient at the bottom of the rib cage. Anatomicallyspeaking, the electrodes are positioned laterally, centered along thepatient's anterior axillary line, and positioned vertically, centered onthe costal margin of the 10^(th) rib. In this manner, the EPSstimulation is focused on the external oblique and the transversusabdominus muscles, thus causing a rapid reduction in both the transversethoracic diameter (side-to-side width) and the sagittal thoracicdiameter (front to back spacing between spine and front of rib cage),causing, in term, a rapid increase in the intrathoracic pressure. Thesewe term the positive pressure thoracic pump EPS (PPTP-EPS) electrodes,because they generate primarily positive intrathoracic pressures duringstimulation. The electrode position of electrode 101 a and 101 b we termthe positive pressure cardiac pump EPS (PPCP-EPS) electrode position.

The stimulation pulses of the PPCP-EPS and PPTP-EPS electrodes may becoordinated (e.g., by an electronic controller) so that the two pulsescoordinate their hemodynamic action to optimize blood flow. Forinstance, by delivering the PPCP-EPS pulse first, then pausing for100-500 milliseconds, and optimally 100-200 milliseconds, then bloodwill be ejected from the heart and the aortic valve will be givensufficient time to close prior to delivery of the PPTP-EPS pulse thatelevates intrathoracic pressure, and causes heightened aortic pressure.Since the aortic valve is more likely to be closed at this point becauseof the optimal inter-pulse timing, then the elevated aortic pressurewill result in forward blood flow, as opposed to retrograde flow backinto the left ventricle had the aortic valve been open.

In some embodiments, it can be beneficial to stimulate inhalation in apatient to provide oxygen to the patient while enabling the rescuer tocontinue to administer chest compressions. One method for electricallystimulating inhalation is by the stimulation of the intercostal musclesas a means of generating negative intrathoracic pressures to causeinspiratory ventilatory action. However, this method is believed to beunreliable. Thus, in order to provide a more reliable ventilatoryaction, electrical stimulations can be provided to promote sternocostalinhalation by stimulating one set of muscles that attach to some portionof the ribs, and by stimulating a second set of muscles that whencontracted cause an opposing motion of the spine in either the sagittalor transverse axis.

More particularly, inhalation may be accomplished by two different setsof muscle action. The primary mechanism for most people is thecontraction of the diaphragm, which increases the volume of the thoraciccavity, thus decreasing the intrathoracic pressure and the intake ofair. Alternatively, a secondary means of increasing the volume of thethoracic cavity is by means of so-called sterno-costal breathing,sometimes also called costal or chest breathing. This breathing mode isoften used during exercise or other anaerobic activity as a means ofaugmenting normal respiratory tidal volumes. Thoracic volume increaseoccurs by the general lifting of the ribs to increase either or both thetransverse thoracic diameter or the sagittal thoracic diameter by thehinging action of the ribs on the vertebral bodies of the spine,specifically at the points of the costal tubercle and the head of therib.

Prior art has described the stimulation of the intercostal muscles as ameans of generating negative intrathoracic pressures to causeinspiratory ventilatory action. This is believed to be a highlyunreliable as a mechanism, as the contraction of the intracostal musclesis as likely to pull down the superior ribs closer to the neck as it isto pull up the inferior ribs closer to the diaphragm. Unfortunately,pulling down the superior ribs actually causes elevated intrathoracicpressure and an exhalation, the opposite of what was intended.

It has been discovered that by stimulating more than one muscle group inparticular combinations and in a time-coordinated fashion, that rib cagecan be elevated to effectuate sterno-costal breathing. As shown in FIG.5, the sterno-costal breathing is promoted by multiple sets ofelectrodes (e.g., 150, 151, and 152) placed on the patient's skin. Theelectrodes can be controlled by control circuitry included in thedefibrillator 208. These electrodes also act as negative pressurethoracic pump (NPTP) mechanism on hemodynamics. In one configuration,anodal electrodes approximately 2 inches in diameter are placed directlyabove the scapula with the circumference of the electrode approximatelycoincident with the inferior angle of the scapula. Each anode (posterioranode left [PAL] and posterior anode right [PAR] 152) is paired with twocathodal electrodes of approximately 2 inches in diameter: the firstcathodal electrode is placed above the rhomboid major muscle (posteriorcathode left rhomboid [PCLR] and posterior cathode right rhomboid [PCRR]151), and the second cathodal electrode is placed above the serratusanterior muscle centered vertically at approximately the fifth or sixthrib (posterior cathode left serratus [PCLS] and posterior cathode rightserratus [PCRS] 150). Electrodes are located on the left side of theposterior of the patient mirror those placed on the right in the figure.Bi-lateral stimulation of the rhomboid major muscles first before theserratus anterior muscles will cause the scapulae to be pinned to thespine, following which bi-lateral stimulation of the serratus will causeincrease in the transverse thoracic diameter increase, intra-thoracicvolume increase, intra-thoracic pressure decrease and sternocostalbreathing. While it is preferable for the rhomboid muscles to bestimulated first, this is not an essential element and the method willstill work with stimulation of the serratus anterior muscles first orsimultaneously.

In general, this method of sternocostal inhalation via EPS works bystimulating one set of muscles that attach to some portion of the ribs,and by stimulating a second set of muscles that when contracted cause anopposing motion of the spine in either the sagittal or transverse axis.Another approach is to place the anodes in the right and left underarmor on the scapula as before, with cathodes placed just inferior tocoracoid processes and along the spine above the trapezius. Cathodalstimulation of the trapezius causes arching of the back, thenstimulation of the electrodes placed by the coracoid processes stimulatethe pectorialis minor, teres major and latissimus dorsi to some extantto cause the ribs to rise primarily to increase the sagittal thoracicdiameter.

Because these NPTP electrodes that are used for increasing thoracicvolume are located primarily posterior, there is no risk of the currentsgenerated during stimulation affecting the rescuer touching the patient.In particular, the benefit is that now the stimulation may be easilyinterposed with the rescuer's manual compressions. Triggering of theNPTP electrode stimulation is preferably timed to occur during theupstroke of the manual compression and will assist with returning thethorax to its natural configuration prior to the next manual compressiondownstroke as well as increase venous return into the atria to improvepre-load hemodynamics.

The EPS electrodes can be incorporated into the harness of a wearabledefibrillator system such as the Lifevest manufactured by ZOLL medical(Chelmsford, Mass.). The EPS electrodes. For example, FIG. 6 shows anexemplary placement of the electrodes 150, 151, and 152 within awearable defibrillator harness.

The three types of EPS pulses for PPCP, PPTP and NPTP may also becombined, either sequentially or simultaneously to enhance hemodynamicsand generate better flow. For instance, a PPCP pulse may be followed bya PPTP pulse followed by a NPTP.

The EPS stimulating waveform itself may be modulated either by pulsewidth modulating the train of pulses or providing a ramped leading edgeto create a more gentle ventilatory cycle for bringing air into thelungs. This will lessen the absolute instantaneous value of theintrathoracic pressure that may be desirous when attempting ventilationas opposed to trying to generate high peak intrathoracic pressures(either positive or negative) for enhanced movement of blood. Morespecifically, the stimulation is a series of high frequency pulses thatmay be delivered by the same circuitry that is used for defibrillation,such circuitry being known to those skilled in the art: a capacitor thatis capable of storing voltages of up to 2000-4000 Volts; a chargingcircuit for charging such a capacitor, typically using a flybacktransformer arrangement; a high voltage, high-speed solid-stateswitching mechanism for connecting the charged capacitor to a patientvia a current carrying cable and patient-attached self-adhesivedefibrillation electrodes. The just-mentioned switching mechanism istypically arranged to provide connection of the capacitor to the patientin both polarities, and is often configured as the classical H-bridgeelectrical switching network topology. During EPS stimulation, thecharging circuit maintains the voltage on the capacitor to a desiredvoltage, typically on the order of 500 Volts. The H-bridge circuit maybe controlled to deliver either a monophasic or biphasic pulse train,though preferably the pulse train is monophasic. The pulses may bepulse-width modulated to deliver a pulse train with the leading edge ofthe pulse train with a duty cycle of as little as 0.1%, and ramping upto a duty cycle of that which is sustained through the remainder of theEPS stimulation. The sustained duty cycle for the EPS stimulation at theconclusion of the ramp may be a duty cycle of as little as 0.1% to asmuch as 100% (i.e. DC). The effective DC value of the waveform duringthe ramp portion of the stimulation may have a linear shape, or may bemore complex, taking the form of an exponential or logarithmic or anarbitrary polynomial. The sustained duty cycle for the EPS stimulationat the conclusion of the ramp may vary over the time course of theinterval during which EPS stimulation is being delivered, since musclefatigue occurs during the typically 30 seconds of EPS stimulation. Forinstance, if the maximum duration for EPS stimulation is set for 30seconds, the sustained duty cycle might be start at 10% for the first 10seconds of the seconds then increasing gradually to 30% over the courseof the remaining 20 seconds.

The individual 100-200 microsecond pulses may be delivered as biphasicpulse pairs. Since nerves and muscles respond to the average voltage ofthe pulse pairs, the average voltage can be ramped by fixing voltage ofthe positive and negative voltages and achieving a zero average voltagewith equal duration positive and negative 100 microsecond pulses. Whilepulses are preferably 100-200 microseconds, they may be as short as 5microseconds or as long as 10 milliseconds for multipulse pulse trainsand as long as 200 milliseconds for single pulse stimulation.

The timing of the EPS stimulations may also be coordinated with an ECGwaveform so that such motions do not occur during the vulnerable periodof the cardiac cycle or are minimized during such period. For example,the defibrillator may be controlled so as to not start a stimulationuntil after the vulnerable period has passed, or can be synchronized tothe R-wave of the ECG but reduce the duration of the stimulation so thatthe compression upstroke does not overlap the vulnerable T-wave. Second,the EPS waveform may also be modulated to reduce the velocities of thethoracic cage as higher velocities may result in re-induction ofventricular fibrillation, particular immediately after thedefibrillation shock and then gradually increase the forcefulness of thestimulation closer to the start of a next shock. In this manner, bloodcirculation may be maximized by providing greater pumping power at theend of a shocking cycle (and also thereby increasing the effectivenessof the next shock), while minimizing the interference with the heart atthe beginning of the cycle when the heart is more vulnerable.

FIG. 7 shows an example system 200, in schematic form, for providingdynamically controlled chest compression to a patient. In general, thesystem 200 involves a number of medical devices that may be used toprovide life-saving care to a victim, such as a victim 202, of suddencardiac arrest. The various devices may be part of a single unit ormultiple units, and may be used to monitor various real-time physicalparameters of the victim 202, to communicate between the components andwith remote systems such as central caregivers, and to provide care tothe victim 202 or provide instructions to caregivers, such as caregiver204, in providing care to the victim 202.

The victim 202 in this example is an individual who has apparentlyundergone sudden cardiac arrest is being treated by the caregiver 204.The caregiver 204 may be, for example, a civilian responder who has hadlimited training in lifesaving techniques, an emergency medicaltechnician (EMT), a physician, or another medical professional. Thecaregiver 204 in this example may be acting alone or may be acting withassistance from one or more other caregivers, such as a partner EMT.

The victim 202 is in a position in which therapy has been provided tothe victim 202. For example, a set of defibrillator electrodes 210 havebeen applied to the victim's torso in a typical manner and are in wiredconnection to a portable external defibrillator 208. The defibrillator208 may be, for example, a typical automated external defibrillator(AED), a professional defibrillator, or other similar type ofdefibrillating apparatus. The victim 202 has also been provided with aventilation bag 206, to provide forced air into the victim's longs toassist in rescue breathing of the victim 202. The defibrillator 208 andventilation bag 206 may be operated in familiar manners and incoordination by various caregivers. Also, the ventilation bag 206 may befitted with various sensors and transmitters so as to communicateelectronically with the defibrillator 208. For example, a volumetricflow sensor may be provided with the ventilation bag 206, and data aboutthe volume of airflow to and from the victim may be passed todefibrillator 208, so the defibrillator 208 may relay such information,or may also use such information to affect the manner in whichdefibrillation is provided to the victim 202.

A computer tablet 214 is also shown communicating with the otherdevices, and being manipulated by caregiver 204. The tablet may serve asa general electronic command post for the caregiver 204 to receiveinformation about the victim 202 and other items, to communicate withother caregivers, and to provide input in controlling the operation ofthe various components in the system 200. The tablet 214 may be providedwith short range and long range wireless communication capabilities,such as Bluetooth or WiFi on the one hand, and cellular 3G or 4G on theother. The caregiver 204 may input information into the tablet computer214, such as information describing the condition of the victim 202 andother similar information that is to be recognized and recorded by thecaregiver 204. The tablet 214 may also be in data communication withmultiple sensors for sensing real-time information about the victim 202,such as blood pressure, pulse, and similar real-time patient parameters.The caregiver 204 may also input information into tablet 214 so as tocontrol one or more of the medical devices being used with the victim202. For example, the user may adjust the type, intensity, speed, orcoordination of treatment that is provided to the victim 202.

Chest compression are delivered manually by the Caregiver 204. In such acase, audiovisual feedback is provided to the Caregiver 204 via Speaker236 a and Display 224. Feedback will direct the Caregiver 204 to delivercompressions less forcefully when necessary.

As shown in this example, multiple different input signals are receivedthat characterize the current real-time condition or physical parametersof the victim 202. For example, an ECG signal 222 may be received by theMPU 212 and may represent current and real time ECG waveforms for thevictim 202, which may be obtained by leads connected to defibrillator208.

An SpO₂ signal 223, or other physiologically-derived signal that iseither a direct or indirect measure of circulatory flow or perfusion, isalso captured at box 224, and may be used to further determine when andat what force to apply chest compressions to the victim 202.

Note that while FIG. 7 shows specific examples of input signals such asSpO2, an apparatus could use any combination of physiological signalssuch as, but not limited to: ECG; measures of cardiac output; measuresof heart rate; blood pressure(s); oxygen saturation (SpO2); heart sounds(including phonocardiography); heart imaging (including ultrasound);impedance cardiography. Compression parameters could use any combinationof features or measurements of compression including, but not limitedto: compression velocity; compression depth; duty cycle; velocity ofdownstroke and upstroke; intrathoracic pressures during compressions;pleural pressures during compressions; sternal position, velocity oracceleration; chest wall or sternal strain or deformation; force appliedto the chest; pressure used to compress the chest by a mechanical chestcompressor.

A signal processing unit 228 is provided to filter inputs, such as ECGinputs, received from the patient for further analysis by theMicroprocessor 230. For example, the signal processing unit 228 mayfilter noise from input signals, and in the case of ECG data may filterartifacts created by chest compression motion of the victim 202 in orderto remove such artifacts. Such preparation of ECG signals may be termedSEE-THRU CPR, and can be performed as discussed in U.S. Pat. No.6,865,413, filed Jan. 23, 2002, and entitled ECG SIGNAL PROCESSOR ANDMETHOD, the teachings of which are incorporated herein by reference intheir entirety.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. The described features can be implemented advantageously in oneor more computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. A computer program is a set of instructions that can be used,directly or indirectly, in a computer to perform a certain activity orbring about a certain result. A computer program can be written in anyform of programming language, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include a local area network (“LAN”),a wide area network (“WAN”), peer-to-peer networks (having ad-hoc orstatic members), grid computing infrastructures, and the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

The computer system may include software for implementing an electronicpatient care record, for example the ePCR software of ZOLL Data Systems(Broomfield Colo.). The software provides the ability to enter, storeand transmit patient information as well as therapeutic interactions.The computer is often a so-called “Tablet” computer system that has beenruggedized for pre-hospital use, but may also take the form of an iPhoneor iPad. Data is preferably transmitted in real time between theportable “Tablet” computer 214 to the MPU 212.

Electromagnetic stimulation may be accomplished via electricalstimulation such as current source or a voltage source known to thoseskilled in the art for use as pacing or defibrillation circuitry.Electromagnetic stimulation may also be accomplished by magneticstimulation accomplished by high current pulses, typically 10 Amps ormore, delivered into magnetic coils placed closed to the muscle groupsneeding to be stimulated. Such systems have been available commerciallyby Cadwell Inc (Device model MES-10).

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the invention. Accordingly, other embodimentsare within the scope of the following claims.

1. A medical system for providing electromagnetic stimulation of apatient, comprising: a sensor positioned to sense the presence of manualchest compressions administered to the patient by a rescuer; and aprocessor arranged to receive data generated by the sensor and detectchanges in the administration of the chest compressions, and circuitryconfigured for delivery of electromagnetic stimulation to the patient tostimulate blood flow in the patient upon detection of the change in theadministration of the chest compressions.
 2. The method of claim 1,wherein the changes comprise a degradation in the quality of the chestcompressions.
 3. The method of claim 2, wherein the degradation in thequality of the chest compressions comprises a change in depth of thechest compressions.
 4. The method of claim 2, wherein the degradation inthe quality of the chest compressions comprises a change in compressionrelease of the chest compressions.
 5. The system of claim 1, wherein theprocessor is configured to detect changes in the administration of thechest compressions by detecting an absence of chest compressions for aperiod of time greater than a threshold.
 6. The system of claim 1,wherein the processor is configured to detect changes in theadministration of the chest compressions by detecting an absence ofchest compressions for a period of time greater than a 2 seconds.
 7. Thesystem of claim 1, wherein the processor is configured to detect changesin the administration of the chest compressions by comparing datagenerated by the sensor during a first time period with data generatedby the sensor during a second time period that occurs after the firsttime period.
 8. The system of claim 1, wherein the sensor is configuredto detect motion of the patient's sternum.
 9. The system of claim 1,wherein the sensor comprises a motion sensor.
 10. The system of claim 1,wherein the sensor comprises a pressure sensor.
 11. The system of claim1, wherein the sensor comprises a velocity sensor.
 12. The system ofclaim 1, wherein the circuitry configured for delivery ofelectromagnetic stimulation is further configured to deliver theelectromagnetic stimulation automatically and without user intervention.13. The system of claim 1, wherein the circuitry configured for deliveryof electromagnetic stimulation comprises an electrode assembly affixedto the patient's thorax.
 14. The system of claim 13, wherein theelectrode assembly is removably affixed to the patient's thorax.
 15. Thesystem of claim 1, wherein the circuitry comprises circuitry configuredto deliver a pulse packet of 100-200 microsecond duration pulses withinter-pulse spacing of 5-15 milliseconds and an amplitude of 300-700volts.
 16. The system of claim 1, wherein the circuitry comprisescircuitry configured to deliver a pulse packet of 20-1000 microsecondduration pulses with a duty cycle of 2-95% and an amplitude of 50-2000volts.
 17. The system of claim 1, further comprising a display deviceconfigured to visually prompt the rescuer to resume manual chestcompressions upon initiation of delivery of the electromagneticstimulation to the patient.
 18. The system of claim 1, furthercomprising a speaker configured to provide an audio prompt the rescuerto resume manual chest compressions upon initiation of delivery of theelectromagnetic stimulation to the patient.
 19. The system of claim 1,wherein the processor is configured to detect changes in theadministration of the chest compressions by detecting a degradation inthe quality of chest compressions.
 20. The system of claim 19, whereinthe circuitry configured to deliver the electromagnetic stimulationsimultaneously with the administration of the manual chest compressionsby the rescuer upon detection of the degradation in the quality of chestcompressions. 21.-26. (canceled)
 27. A medical system for providingelectromagnetic stimulation of a patient, comprising: a first set ofelectrodes configured to be located to initiate blood flow based on acardiac pump mechanism; a second of electrodes configured to be locatedto initiate blood flow based on a thoracic pump mechanism; and acontroller programmed sequence delivery of electrical energy from thefirst set of electrodes and the second set of electrodes to generatedual-stage electrical stimulation configured to cause blood flow in thepatient.
 28. The system of claim 27, wherein the dual-stage electricalstimulation comprises a first stage during which the controller isconfigured to activate the first set of electrodes and a second stageduring which the controller is configured to activate the second set ofelectrodes.
 29. The system of claim 27, wherein the second set ofelectrodes are configured to be positioned at locations that primarilystimulate thoracic muscle groups that during contraction produce bloodflow primarily via the thoracic pump mechanism.
 30. The system of claim29, wherein the second set of electrodes are configured to be positionedon the left and right sides of the patient at the bottom of the ribcage.
 31. The system of claim 27, wherein the controller is furtherprogrammed sequence delivery of electrical energy from the first set ofelectrodes and the second set of electrodes by delivering a pulse fromthe second set of electrodes 100-500 milliseconds after delivering apulse from the first set of electrodes.
 32. The system of claim 27,wherein the controller is further programmed sequence delivery ofelectrical energy from the first set of electrodes and the second set ofelectrodes by delivering a pulse from the second set of electrodes100-200 milliseconds after delivering a pulse from the first set ofelectrodes.
 33. A method for promoting sternocostal inhalation,comprising: electrically stimulating a first set muscles that attach tosome portion of the ribs; and electrically stimulating a second set ofmuscles that when contracted cause an opposing motion of the spine. 34.The method of claim 33, wherein electrically stimulating the second setof muscles causes an opposing motion of the spine in either the sagittalor transverse axis.
 35. The method of claim 33, wherein electricallystimulating the first set muscles comprises electrically stimulating thefirst set muscles using a first cathodal electrode located above theright rhomboid major muscle and a second cathodal electrode locatedabove the left rhomboid major.
 36. The method of claim 34, whereinelectrically stimulating the first set muscles further compriseselectrically stimulating the first set muscles using an anodalelectrodes located above the scapula.
 37. The method of claim 33,wherein electrically stimulating the second set of muscles compriseselectrically stimulating the second set of muscles using a firstcathodal electrode located above the left serratus anterior muscle and asecond cathodal electrode located above the right serratus anteriormuscle.
 38. The method of claim 33, wherein electrically stimulating thesecond set of muscles comprises electrically stimulating the second setof muscles at a time subsequent to electrically stimulating the firstset muscles.
 39. The method of claim 33, wherein electricallystimulating the first and second sets of muscles comprises electricallystimulating the first and second sets of muscles during an upstroke of amanual chest compression.
 40. The method of claim 33, whereinelectrically stimulating the first and second sets of muscles compriseselectrically stimulating the first and second sets of muscles using apulse width modulated waveform.
 41. The method of claim 33, whereinelectrically stimulating the first and second sets of muscles compriseselectrically stimulating the first and second sets of muscles using awaveform comprising a ramped leading edge.
 42. A method for providingelectromagnetic stimulation of a patient, comprising: providing signalsvia an interface to sequence delivery of electrical energy from a firstset of electrodes configured to initiate blood flow based on a cardiacpump mechanism and a second set of electrodes configured to initiateblood flow based on a thoracic pump mechanism to generate dual-stageelectrical stimulation configured to cause blood flow in the patient.